We continue to explore the rules governing formation of ordered retinotectal connections during Xenopus development. Using a variety of histological, electron microscopic, and autoradiographic procedures, we are tracing optic pathways during normal development, regeneration and after eye rotation or compound eye formation, etc. Visuotectal recordings are correlated with the organization of optic pathways in retina, optic nerve, and tract. we are testing a spatio-temporal model of connectivity to determine whether simple morphogenetic rules governing cell birth and axon outgrowth could account for the formation of ordered neuronal arrays.